Convert to USES=kmod, which removes duplicated code and ensures that all
required steps are followed.
There are no user-visible changes. The exception is multimedia/ptx-kmod,
which now installs the kernel module into /boot/modules instead of
${PREFIX}/libexec/${PORTNAME}, this was something USES=kmod cannot handle.
PR: ports/183625
Submitted by: myself
Approved by: portmgr (bdrewery)
Exp-run by: bdrewery